Good topic idea.
I'll list my most common ones as well:
Ball Lightning: I actually think this spell might be a little TOO good (seems EVERYONE uses it). I use it because there are so many robots in the game, and it's good for it's nice damage and knockback. There also arent much in the way of other Air element attacks....
Energy Orb: Similar reasons as Ball Lightning; this is also one I might use when I want to hit something with a spell that DOESNT cause knockback.
Plasma Bolt: If I'm NOT using Energy Orb on a continent, chances are I took this one instead. Nice light element attack with a good fire rate.
Fire Shield: I know these can be abused, but I utterly refuse to use them that way. I'll turn this on in quick, short bursts, to deal with attacks that I'm certain I cannot dodge. Quick blocking, in other words, which I suspect is the intended use (as opposed to having them on for silly amounts of time). Also used to get past jumping spikes in crowded corridors.
Ride the Lightning: Extra jump..... enough said.
Storm Dash: Does anyone NOT use this?
Forest Rage: Basic earth attack, nice solid shot, slides on stuff. Useful.
Fireball: Again, another good basic attack, useful in many situations. I seem to end up in the Shallows or Ocean alot, so this is a necessity against things like the Jellyfish bosses, or those horrible Whales.
Light Snake: VERY useful in caves. Usually the very first spell I go after.
Flash of Light: I hate using Light Orb or whatever it's called; the bloody things are too small and need to be dropped all over the place. I use Moon Lamps usually..... until I can get Flash of Light to Tier 2 or 3 (usually 3), at which point it becomes crazy useful. Easily one of the best spells in the game. Requires coral though.....
Storm Fist: Swimming!
Insect Orb: Ooh, I loooooooooove this one. This is my favorite spell right now. This went from "totally useless" in 1.0, to "I NEED TO HAVE THIS" in 1.1. Very powerful. It's useful as a defensive thing, for popping enemies that get too close, as it hits REALLY fast, it's useful as a basic attack, as it does good damage, it's useful for smashing background entities.... even against Slimes (FINALLY a good way to kill those!), and it has a very interesting and unique quality to it: The larger the target is, THE MORE DAMAGE THIS CAN DO. This being because every individual insect collides seperately with enemies and objects. The more that connect at once, the more damage you get. T-Rexes, for instance, will fall in a single blow from this, because you can smack them with so many insects at once (AND they're weak to Earth). Giant Wasps too; a tactic I like to use against them is a quick Shield flare, where I then crash into the wasp and fire Insect Orb; sometimes this will kill the thing instantly, other times it takes two hits (this is on high difficulties, too). I also use this against those fire seekers that dragons and Overlords love using.
Ice Burst: Very strong water melee spell that actually has a nice amount of range to it.
Ice Cross: Similar to Ice Burst. Good at smacking ground foes.
Tidal Pulse: unique among the straight-shot spells in that it not only travels slowly, but can also be fired rapidly. This one actually has quite alot of uses. One of the first spells I go after. Also amazing against those Nightmare Octopi!
Cleft Smoglet: Fires in two directions, does Entropy damage, and can be fired REALLY REALLY FAST.....this has way more use than I'd originally thought it would. I use this one pretty often. Against certain types of targets, this is just wonderful.
Flamethrower/Geyser: Great for wrecking background things and those damn lions. The bit where it adds a weakness is very useful as well.
Sunrise/Moonrise: Obvious usage. Sunrise is also great just to light up outdoor areas without having to recast Flash of Light every 30 seconds.
Dire Butterfly: TRYING TO FIGURE OUT WHAT THIS IS FOR. I havent succeeded in this yet.
I know that's alot, but I really do use all of those spells. Some others (like Rockslide) I havent experimented enough with. And I dont always use exactly this build, I'll sometimes mix it up a bit on each continent. I find myself rarely using the Teleports, or Lightning Rocket. For my playstyle, they really arent needed.
